Device and method for the axial forming of elongated hollow bodies

ABSTRACT

A device and a method for axially forming an elongated hollow body is disclosed. The device has at least one receptacle, a reducing die, a punch for pressing the elongated hollow body through the reducing die in the direction of an axis, an expanding mandrel and means for limiting the axial displacement of the punch. The punch and the expanding mandrel are movable on the same axis and the expanding mandrel is arranged inside the punch. The hollow body is reduced to a first diameter in a first portion and expanded to a second diameter in a second portion as a result of a movement of the punch and the expanding mandrel in the same direction.

BACKGROUND

The present invention relates to a device and to a method for axially forming an elongate hollow body.

It is generally known in the prior art that pipes can be either expanded or reduced in diameter at their ends in one working process. Here, pipes, or elongate hollow bodies, are, however, formed in two working processes which take place separately from one another, which working processes take place either on different machines or require a set-up process in order to be able to use the respectively required tool sets.

Therefore, there exists a need for a device and a method for axially forming an elongate hollow body, in order to produce workpieces using the processes of expansion and reduction in one working process, such that it is possible to save on a second set of tools, working time, set-up time and also machine time.

SUMMARY

A device according to the features of patent claim 1 and a method according to the features of patent claim 3 are disclosed. Further advantageous refinements of the device and method are specified in the dependent patent claims. It is pointed out that the features specified individually in the dependent patent claims may be combined with one another in any desired technologically expedient manner and define further embodiments of the disclosure. Furthermore, the features specified in the claims are specified more precisely and explained in the description, with further exemplary embodiments being presented.

More specifically, a device for axially forming an elongate hollow body, is disclosed. The device comprises a reduction die for leading through the elongate hollow body, a ram for pushing the elongate hollow body through the reduction die in the direction of an axis, an expansion mandrel and a mechanism for limiting the axial movement of the ram. The ram and the expansion mandrel are movable on the same axis and the expansion mandrel is arranged within the ram.

Such a device is suitable for producing elongate hollow bodies, in particular pipes, wherein the workpieces may also have structures which are already provided or which may be produced as a result of the workpieces being pushed through the reduction die and/or as a result of the expansion by the expansion mandrel. In particular, it is possible in this way for the hollow body to be reduced to a first diameter in a first portion and expanded in a second portion to a second diameter as a result of a movement of the ram and the expansion mandrel in the same direction.

Here, in one exemplary arrangement, the ram may be formed in the manner of a cylinder or similar hollow body and have a central axis, which regularly corresponds to the movement axis. Now provided coaxially and/or parallel with respect to the axis is (at least) one expansion mandrel, which extends into a corresponding cavity of the ram. In one exemplary arrangement, the ram and expansion mandrel are formed coaxially with respect to one another. The expansion mandrel advantageously projects out of the ram in the “inserted” state, such that the expansion mandrel forms an upstream radial support for the elongate hollow body in a first forming process. For the relative movement of the ram and expansion mandrel, it is possible to provide separate or common drive units which are operated by a controller (and if appropriate, with the use of sensors). The axial movement of the ram may be limited based on different structural or control concepts, such as, for example, possible to provide a motor, a stop, a feed motion limiter, a brake, a latching lug, a damper or the like, in order to stop the ram at a predefined time (and/) or movement travel.

To obtain higher true strains, it is possible for both the receptacle for the workpiece and also for the reduction die to be heatable, such that the workpiece may basically (and preferably) be formed in the cold state, but if appropriate also in the semi-warmed or warmed state. In the case of semi-warmed forming, at least the range of blue brittleness (approximately 400° C.) should be overcome, with it preferably being possible to operate in the range of 700-800° C. Warmed forming is carried out above temperatures of at least 1100° C. Therefore, it is in particular also proposed that the expansion mandrel and/or the ram and/or the reduction die and/or a receptacle for the elongate hollow profile be heatable.

According to one refinement of the device, it is proposed that the expansion mandrel is movable independently of the ram. It is therefore possible for the workpiece to be divided into first and second portions of any desired length. Here, the ram pushes the hollow body through the reduction die until a predetermined length of a first portion is reached. At the same time, or else after the movement of the ram has ended, the expansion mandrel is moved further such that the workpiece is expanded over the predetermined length of a second portion proceeding from that end of the workpiece, which is connected to the ram or the expansion mandrel. Here, the expansion mandrel need not necessarily be pushed so far that the workpiece fills out the gap between the expansion mandrel and the reduction die, but rather may be stopped before said point. This would result in an intermediate portion between the first and second portions, the intermediate portion corresponding substantially to the shape of the original workpiece. By filling out the gap between the expansion mandrel and the reduction die, however, the transition between the first and second portions can be calibrated such that the workpiece can if appropriate be pressed into provided wall structures and therefore formed further.

A method for axially forming an elongate hollow body is also disclosed. In one exemplary arrangement, a ram and an expansion mandrel is moved in the same direction, and the hollow body is reduced to a first diameter in a first portion during a first process and is expanded in a second portion to a second diameter during a second process.

According to one refinement of the method, during the first process, a parallel movement of the ram and of the expansion mandrel takes place within a receptacle for positioning the elongate hollow body, wherein the ram pushes the elongate hollow body into a reduction die. It is thus, for example, the case here that, in the first process, the ram is moved in the direction of the axis longitudinally as far as the reduction die, wherein the expansion mandrel can fix the ram, or the hollow body to be formed, in the desired position. Here, the workpiece (hollow body) is pushed (partially) through the reduction die with the required force, wherein at the same time, a reduction of the previous (starting) diameter of the workpiece takes place in the contact region of the reduction die and workpiece.

It is particularly advantageous for the processes of the expansion and of the reduction of the diameters of the hollow body to be carried out in succession. Accordingly, once the desired reduction has been attained over the first portion, the first process ends and the second begins preferably directly thereafter, such that an uninterrupted forming process takes place.

In one exemplary arrangement, during the second process, only an axial movement of the expansion mandrel is carried out until the expansion mandrel extends at least partially into a reduction die. While the ram now moves no further and rests in the receptacle, the expansion mandrel (if appropriate, also a profiled mandrel) alone is moved further longitudinally in the direction of the reduction die. Here, the expansion mandrel is forced into the workpiece and expands the latter to such an extent that its circumferential surface comes to bear against the receptacle.

In particular, it is accordingly the case that the ram acts on the elongate hollow body axially and the expansion mandrel acts on the elongate hollow body radially from the inside. This takes place preferably in two separate successive processes, but it is likewise possible for the processes of reduction (first process) and expansion (second process) to be combined.

Furthermore, the invention encompasses the use of a hollow body produced by the device proposed here, or produced according to the method presented here, for transmitting torque in a motor vehicle. Consideration is given here in particular to longitudinal shafts in the drivetrain of motor vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is explained in more detail below on the basis of the figures. It is pointed out that while the figures show particularly exemplary design variants of the disclosure, the disclosure is, however, not restricted to the designs shown in the drawings. In the drawings, in each case it is shown schematically:

FIG. 1 is a cross section of a design variant of a device for axially forming an elongated hollow body,

FIG. 2 is a cross section of the device from FIG. 1 during a reduction of a diameter of a workpiece,

FIG. 3 is a cross section of the device from FIG. 1 during a subsequent expansion of the diameter, and

FIG. 4 is a representation of a drivetrain of a motor vehicle having a longitudinal shaft.

DETAILED DESCRIPTION

The present invention is not restricted to the exemplary embodiments illustrated. In fact, numerous modifications of the invention are possible within the scope of the patent claims. It is thus also possible in particular to use rotationally asymmetrical receptacles, reduction dies, rams or expansion mandrels to produce likewise rotationally non-symmetrical workpieces. Furthermore, the workpieces may be profiled or processed as a result of a profiled reduction die or profiled expansion mandrel and a correspondingly matched receptacle shape.

FIG. 1 schematically shows the cross section of a device 1 for axially forming an elongate hollow body 2, with the hollow body 2 being placed or inserted into a receptacle 3 at the start of the process. Here, a ram 5 and an expansion mandrel 6 are not in engagement with the hollow body 2, but may already be positioned or guided, at least partially, in the receptacle 3. Here, the expansion mandrel 6 is guided within the ram 5 and is in particular movable independently of the ram 5 on the same axis 7.

The device 1 also has a reduction die 4 which is arranged at one end of the device 1 opposite the engagement opening of the device, where the ram 5 and of the expansion mandrel 6 are positioned. In particular, the reduction die 4 has an opening 18 with a tapering or reducing cross section (for example in the manner of a cone 19 or a chamfer), with the workpiece being provided (at least in the region to be formed) with a starting diameter which is greater than the smallest cross section of the reduction die.

To obtain higher true strains of the workpiece, the device 1 may be designed such that it is heated or can be warmed in order to enable forming at relatively high temperatures. Here, components of the device 1 may be brought up to corresponding temperatures for example by means of induction, a flow of a heating medium through the device 1, electrical heating elements etc. Furthermore, the hollow body 2 may be placed into the receptacle 3 having already been pre-warmed. It is additionally possible for at least one element of the group comprising receptacle 3, reduction die 4, ram 5 and expansion mandrel 6 to be heated or warmed.

FIG. 2 schematically shows the cross section through the device 1 during a first process, with the ram 5 being in engagement with the hollow body 2 and pushing the latter towards the reduction die 4 such that, in the first portion 9, the starting diameter of the hollow body 2 is reduced to a first diameter 10. In said first process, the ram 5 and expansion mandrel 6 are moved together and push the hollow body 2 through the reduction die 4 together.

FIG. 3 schematically shows the cross section of the device 1 for axially forming the elongate hollow body 2 during a second process, with the expansion mandrel 6 now being moved independently of the ram 5 and, in a second portion 11 of the elongate hollow body 2, expanding the workpiece 2 to a second diameter 12 which is greater than the starting diameter of the workpiece. Here, the ram 5 is stopped in terms of its axial movement. In one exemplary arrangement, a feed motion limiter 8 (for example a correspondingly controlled motor), shown only schematically here, serves to sop the axial movement of the ram 5. In particular, the expansion mandrel 6 is moved until it abuts against the reduction die 4, such that a calibrated transition between the first diameter 10 and the second diameter 12 of the hollow body 2 is obtained.

To remove the workpiece 2, it is possible firstly for the receptacle 3 and the reduction die 4 to be opened; it is secondly possible for the reduction die 4 to be released from the receptacle 3 such that the finished hollow body 2 may be removed from the receptacle 3 along the axis 7. At the same time, the ram 5 and/or the expansion mandrel 6 may be used as an ejector. It is however in particular also possible for the ram 5 and expansion mandrel 6 to be retracted into the starting position, and the workpiece removed either through the opened reduction die 4 or through the opened receptacle 3.

FIG. 4 now shows an exemplary field of use of the hollow profiles 2 produced in this way, in a motor vehicle 13. Here, the hollow profiles are used for example as so-called longitudinal shafts 15 in the drivetrain 14 of a motor vehicle 13, in order to transmit torque, which is generated by a drive, to remote wheels 17. 

1. A device for axial forming of an elongate hollow body, comprising: a reduction die for leading through the elongate hollow body, a ram for pushing the elongate hollow body through the reduction die in the direction of an axis, an expansion mandrel, and a mechanism that limits the axial movement of the ram, wherein the ram and the expansion mandrel are movable on the same axis and the expansion mandrel is arranged within the ram.
 2. The device as claimed in claim 1, wherein the expansion mandrel is movable independently of the ram.
 3. A method for axial forming of an elongate hollow body, comprising: moving a ram and an expansion mandrel in the same direction such that the elongate hollow body is reduced to a first diameter in a first portion during a first process, and is expanded in a second portion to a second diameter during a second process.
 4. The method as claimed in claim 3, in which during the first process, a parallel movement of the ram and of the expansion mandrel takes place within a receptacle for positioning the elongate hollow body, wherein the ram pushes the elongate hollow body into a reduction die.
 5. The method as claimed in claim 3, in which the processes of the expansion and of the reduction of the first and second portions of the hollow body are carried out in direct succession.
 6. The method as claimed in claim 3, in which during the second process, only an axial movement of the expansion mandrel is carried out until the expansion mandrel extends at least partially into a reduction die.
 7. The method as claimed in claim 3, in which the ram acts on the elongate hollow body axially and the expansion mandrel acts on the elongate hollow body radially from the inside.
 8. (canceled)
 9. The device as claimed in claim 1, wherein the device further comprises a heating element operatively connected thereto.
 10. The device as claimed in claim 9, wherein the heating element is operatively connected to at least one of the reduction die, ram and expansion mandrel.
 11. The device as claimed in claim 1, wherein the device further comprises a receptacle for receiving the hollow body, the receptacle defined by an engagement opening that is configured to receive the ram and expansion mandrel.
 12. The device as claimed in claim 11, wherein the reduction die is positioned at an end of the receptacle, opposite the engagement opening.
 13. The device as claimed in claim 1, wherein the reduction die is defined by a first opening having a first diameter, a tapered portion, and a second opening defined by a second diameter.
 14. The device as claimed in claim 1, wherein the mechanism is a feed motion limiter.
 15. The device as claimed in claim 1, wherein the reduction die is selectively removable from the device so as to release the hollow body from the device.
 16. The method as claimed in claim 4, further comprising heating the receptacle.
 17. The method as claimed in claim 6, further comprising heating the reduction die.
 18. The method as claimed in claim 3, further comprising heating at least one of the ram and the expansion mandrel.
 19. The method as claimed in claim 4, further comprising heating the hollow body prior to placing the hollow body within the receptacle.
 20. The method as claimed in claim 4, further comprising selectively separating the reduction die from the receptacle after the second process to release the hollow body. 